It's called a "loot box" - a device in video games that unlocks random rewards like changing their character's appearance or giving them more powerful weapons to use.
While that sounds like harmless, run-of-the-mill gaming, there's a worrying catch: players are often using real cash to open these virtual treasure troves.
And, just like a pokie machine, making a payment doesn't guarantee the goodies, compelling players to up their chances by spending more of their own money.
Their inclusion in games like Overwatch, FIFA 18, Madden N.F.L. 18 and Star Wars Battlefront II has already drawn sharp criticism, spurring developers to leave them out of new products.
Now Kiwi and Australian researchers who investigated loot boxes say they're "psychologically akin" to many forms of gambling - raising the question of whether anyone under the age of 18 should be allowed to play games that contain them.